4.1 Atoms and isotopes

The plum pudding model of the atom was replaced by the nuclear model after the alpha particle scattering experiment.

Table 1 shows three descriptions of the structure of an atom.

Description	Label
Electrons occupy discrete circular orbits at fixed, quantized energy levels around a central positive nucleus.	P
The atom is a uniform sphere of positive charge with small, negatively charged electrons distributed throughout it.	Q
A tiny, dense, positively charged nucleus is situated at the centre, with electrons orbiting in the vast empty space around it.	R

Which label (P, Q, or R) describes the plum pudding model?
What is the correct chronological order of these models, from earliest to most recent?

[2]

During the alpha particle scattering experiment, positively charged alpha particles were fired at a thin metal foil.

Complete the following sentences. Choose your answers from the options below:

\text{attracted to, } \text{repelled by, } \text{increases, } \text{decreases, } \text{remains constant, } \text{stronger, } \text{weaker}

Since both the incoming alpha particle and the target gold nucleus carry positive charges, the alpha particle is ____________________ the gold nucleus.
As an alpha particle moves closer to the gold nucleus, the electrostatic force acting on the alpha particle ____________________.
If a silver foil (atomic number $Z = 47$ ) were used instead of gold foil (atomic number $Z = 79$ ), the electrostatic force of repulsion experienced by an alpha particle at any given distance would be ____________________.

[3]

Another research group in a different laboratory carries out the same scattering experiment using different equipment and obtains consistent results.

Which term describes measurements that yield consistent results when obtained by a different investigator using different equipment?

[1]

Description

Label

Electrons occupy discrete circular orbits at fixed, quantized energy levels around a central positive nucleus.

The atom is a uniform sphere of positive charge with small, negatively charged electrons distributed throughout it.

A tiny, dense, positively charged nucleus is situated at the centre, with electrons orbiting in the vast empty space around it.

During the alpha particle scattering experiment, positively charged alpha particles were fired at a thin metal foil.

Complete the following sentences. Choose your answers from the options below:

\text{attracted to, } \text{repelled by, } \text{increases, } \text{decreases, } \text{remains constant, } \text{stronger, } \text{weaker}

Since both the incoming alpha particle and the target gold nucleus carry positive charges, the alpha particle is ____________________ the gold nucleus.
As an alpha particle moves closer to the gold nucleus, the electrostatic force acting on the alpha particle ____________________.
If a silver foil (atomic number $Z = 47$ ) were used instead of gold foil (atomic number $Z = 79$ ), the electrostatic force of repulsion experienced by an alpha particle at any given distance would be ____________________.

4.1 Atoms and isotopes

4.1 Atoms and isotopes Questions